In order to solve the problem, it is necessary to apply the concepts related to the conservation of momentum, especially when there is an impact or the throwing of an object.
The equation that defines the linear moment is given by

where,
m=Total mass
Mass of Object
Velocity before throwing
Final Velocity
Velocity of Object
Our values are:

Solving to find the final speed, after throwing the object we have

We have three objects. For each object a launch is made so the final mass (denominator) will begin to be subtracted successively. In addition, during each new launch the initial speed will be given for each object thrown again.
That way during each section the equations should be modified depending on the previous one, let's start:
A) 



B) 



C) 



Therefore the final velocity of astronaut is 3.63m/s
Rocks and sediments I believe
The study of motion is called kinematics.
Answer:
Th-234, Pa-234
Explanation:
In alpha decay, 2 protons and 2 neutrons are lost. So U-238 would become Th-234.
In beta decay, one neutron is turned into a proton. So Th-234 would become Pa-234.
Answer:
Explanation:
The definition of acceleration is the change in velocity over a period of time. If the girl's velocity is constant, that means it's not changing. Therefore, acceleration is 0 m/s/s